UK Independence Party (UKIP) leader Nigel Farage says Britain’s upcoming referendum on EU membership is a vote on whether the UK wants to enter political union with Turkey, a state he described as “increasingly Islamist and authoritarian.”

Farage made the remarks in a speech to fellow MEPs in Brussels, during which he also accused Turkey of blackmailing the EU into accepting its proposals to address the ongoing migrant crisis.

The comments come after the EU agreed to speed up Turkey’s accession process to the EU and pay Ankara €3 billion (US$3.3 billion) in aid in return for the country accepting tens of thousands of extra refugees.

EU leaders also laid out plans to allow Turkish nationals to travel to the EU visa-free by June 2016.

Farage told MEPs on Wednesday that if Turkey joined the EU it would make Britain more vulnerable to terrorism.

“The historic error made by Chancellor Merkel last year by saying all can come has led directly to this mess and now we are being blackmailed by Turkey. I wish that David Cameron was as good at negotiations as the Turks are,” he said.

“So we are going to go into political union with a country that has got borders with Iraq, Iran and Syria, a country that is poorer than anybody else in the European Union and give free movement to 75 million people. And join up with a government that is increasingly Islamist and authoritarian.

“Well this referendum in Britain is all about what is the safest option. It is pretty clear to me that a vote to remain is a vote for Turkey, a vote to remain is a vote for massively increased immigration into Britain and a vote to remain is a vote that makes Britain more vulnerable to terrorism. It is safer to vote to leave and take back control of our borders,” he added.

Former Shadow Home Secretary David Davis also warned about the security implications of Turkey joining the EU.

“This demonstrates only too clearly why our membership of the EU, far from improving our security, actually puts it at greater risk,” the former shadow home secretary concluded.

The United Nations expressed concern about the EU/Turkey deal, highlighting a proposal to send Syrian refugees back from Greece to Turkey.

According to the plan, a refugee in Turkey is settled in the EU for every Syrian that is deported.

“We hope that individuals returned to Turkey who have specific resettlement needs, such as family reunification, would be considered for the resettlement/admission program to the EU,” said the Office of the UN High Commissioner for Refugees (UNHCR).